The present invention relates to the field of propeller blades for aircraft, such as the blades present on turboprops.
Propeller blades for turboprops are generally made of a metal material. Although propeller blades made of metal material present good mechanical strength, they nevertheless present the drawback of being relatively heavy.
In order to obtain propeller blades that are lighter, it is known to make propeller blades out of composite material, i.e. by making structural parts out of fiber reinforcement with a resin matrix.
The technique generally used consists in forming a stack of preimpregnated unidirectional sheets or plies (draping) that is placed in a mold with the successive plies being given different orientations, prior to compacting and polymerizing in an autoclave. An example of how a propeller blade can be made by that technique is described in particular in document U.S. Pat. No. 6,666,651.
That technique is very difficult and requires the ply stacking operations to be performed manually, which is lengthy and expensive. In addition, the stratified structure is not optimal, in particular concerning shocks or impacts that may give rise to delamination.
Document EP 1 526 285 describes a more effective method of fabricating a turbine engine blade out of composite material, the blade being fabricated by three-dimensionally weaving a fiber preform and densifying the preform with an organic matrix. That method makes it possible to obtain blades that present very great mechanical strength, in particular against shocks or impacts, without any risk of delamination. Nevertheless, propeller blades of large dimensions made using that technique still present relatively great weight. Unfortunately, in order to improve the performance of turboprops, in particular in terms of fuel consumption, it is desired to reduce weight.